Metallurgical process



Jan. 8 1924.

W. E. GREENAWALT METALLURG I CAL PROCES S Original Filed April 16, 1918 (ICQ/bodes @wm/MMM,"

Patented Jan. 8, 1924.

PATENT ori-Ica WILLIAM E. GREENAWALT, OF DENVER, COLORADO.

METALLURGICAL PROCESS.

Application led April 16, 1918, Serial No. 228,952. Renewed March 7, 1921. Serial No. 450,460.

To all whom it may concern:

Be it known that I, WILLIAM E. Gnnnnli- WALT, a citizen of the United States, residing in the city and county of Denver and State of Colorado, have invented certain new and useful Im rovements in Metallung-ical Processes, of which the following is a specification.

The invention relates more particularly to the extraction of copper from its ores by solvent processes, in which the solventis reffenerated by electrolysis.

t is Well known that oxidized ores of copper are readily soluble in acid solutions and that the sulphide minerals' are hardly effected thereby. Ferrie salts readily dissolve the copper from its oxide minerals, and also quite readily dissolve the copper from the sulphide minerals, especially from chalcocite and chalcopyrite. The objection to ferrie salt solutions has been, that, in dissolving the copper much of the iron is eliminated. as a basic salt; that the acid required for regeneration of the solvent is not readily available; that electrolytic deposition of the copper from solutions strong in iron is dilcult; and that the regeneration of the ferric salt, in any case, can not, ordinarily, be effectively accomplished. It is the object of this process to so eliminate, or modify, these difficulties, to make an economical working process, especially on ores low in copper and containing a large amount of injurious impurities.

If an acid solution of ferrie sulphate is applied to a mixed oxide and sulphide ore, the reactions may be represented as follows:

The copper goes into solution, While the ferrie iron is reduced to the ferrous condition. It is desirable to use a solution high in iron, to dissolve the copper, if the ferrie sulphate is to be effectively applied. Such '.f-folutions, especially if lean in copper, are not readily precipitated electrolytically. They may be precipitated with iron, but with iron precipitation, both the iron and the combined and uncombined acid are irrecoverably lost. Besides, the iron is expensive and not always obtainable at cop-- per mines. In my present process, I precipitate the copper with hydrogen sulphide, generated by the action of acid on iron matte, thus:

The hydrogen sulphide is applied to the so lution to precipitate the copper as the sulphide, with the simultaneous regeneration of an equivalent of acid:

5.- CuSOd-HESICuS-i-HZSOy The acid so generated, effectively acts to retain the iron in the solution, and makes the effective regeneration of the ferrie salts ossible. Some of the iron Will inevitably e lost, either by the oxidation to an insoluble form, by the formation of basic salts, and by the wash waters which are too'lean to be added to the solvent. To supply this deficiency, I introduce the ferrous salt formed in the hydrogen sulphide generation, into the solution for the copper. This residue from the generation of the hydrogendsulphide usually also containssome free acl After the copper has been precipitated, and the ferrous salt from the generation of the hydrogen sulphide added to the solution, all the iron is in the ferrous condition, and as such, is not available for the solution of the copper from the ore. Ferrie sulphate dissolves copper; ferrous sulphate does not. In order to convert the ferrous iron into the ferrc iron, the solution is electrolyzed, and the acid regenerated in the precipitation of the copper, as set forth in equation 5, makes effective electrolytic regeneration of the ferrie salts possible, as shown by equation:

6. 2FeSO,+H2SO,-{-electrolysis:

Fe2(SO4)3 l-H2 or 7. QFeSOd-HZSOEPO-l-electrolysis:

Fe2(SOi)3+H-0 It would be quite possible, if desired, to electrolyze a neutral solution of ferrous sulphate, but in such an event some of the iron would be lost as the oxide and some as ore contains,v precious metals, the precious metals are extractable with the copper. There is also some advantage in electrolytically converting the ferrous-chloride :to the ferrie chloride, in that carbon anodes can be` usedfandV the; nascent chlorineliberated at the anodel acts ymore effectively than` ordi-` nary chlorine in raising the valeney ot the ferrous salts, Then, too, the ferrous chloride, actin as a depolarizer,`tends to materially rec 'uce the E'. M'. Fi required in\ the electrolysis. Effective agitation, during electrolysis, isdesirable; this not only aids the depolarization, hutV also the oxidation, or adduction, ofthe ferrous` salts. lt has been observed that carbon electrodes give a better depolarization, and consequently a lower E. M. F: than lead, ferro-silicon, or in agnetitey electrodes. lfL oai-bon anodes are used in a sulphate solution, there is danger of excessive anode disintegration. @n the other hand; carbon anodes are quite" durable in chloride solutions, especially in acid chloridesolutions, andx in solutions containing large quantities of ferrous salts Which malte possible a-highleiiieiency'in depolarization. i i

The following react-ion Willy explain the steps quite clearly when chloride solutions are used, containing` ferrie chloride toA efrtract the copper. lffthe feriricchloridesoho tion is appliedI to the ore, thecopper goes into the solution as the chloride, While the ferrie chloride is reduced tothe ferrous conditionz e. ouoi'ereor: nourrisson..

9. Cii2S-l-4FeCl3:QCuGl-l-iletll2-S.,

` ride 13. lleCl,-l-lrlCl-l-electrolysis:FeClS-i-H. 14. ltiCl-l-electrolysiszH-l-Cl. y 15. FeCl-l-ClzlfeCl. 16. BlTeCl-I-SHZO-i-electrolysis:

FeCl-kllegOg-tll.

'lhis regenerated ferrie chloride solution is then again returned to the ore to pass through another cycle. The ferrous iron from the hydrogen sulphide generator may be addedl to the leaching solution and thel ferrous iron regenerated with the rest of the ferrous iron. used in: leaching,l it is desirable to use considerable sodium chloride;` this assists in keepingsilver chloride and cuprous chloride in solution, Which otherwise would not be readily soluble. rlhe regenerated. sulphur-ic acid reacts with the sodium.. chloride to form.

hydrochloric acid. lt Willv he seen that the acid regenerated` in the precipitation of the copper and' the reduction of the variable valent salts, playsan important part in the regeneration ofthe ferrie salts.

This process is somewhat of an inversion of the usually proposed methods of precipitating and electrolyzing copper solvents, in that the electrolysis is performed after the copper is precipitated, instead of attempting toprccipitatethe copper electrolytically With the simultaneous regeneration ofi the solvent. There are, however, certain very marked advantages in this apparently duplication of methods: rst, acid is usually very expensive in mining districts and this method suppliesv an abundance of acid.; second, if chloride solutions are used, it permits of the extraction of the precious metals with the copper, as also much of the lead, 'if 1.'.

present: third, the chemical precipitation in. addition to regenerating an, abundance of acid, leaves the iron in the ferrous condition, and this iron is an elfective depolarizer in the clectrolytic generation of the ferrie salts, Y l" thus greatly reducingthe E. M. F. required in the operation: fourth, it permits of the use of carbon anodes in the production of the ferrie salts: fifth, it permits of effective electrolytic generation of ferrie salts, Which is not possible, or at least advisable, simultaneously with the deposition of the copper: sixth, the foulness of the solution is pra@ tically immaterial, and a high iron content is desirable, not only in leaching with fe .i salts, but in the electrolytic regeneration of the ferrie salts: seventh, both the iron and the acid used inthe production. of the `hydrogen sulphide for the precipitation of the copper may be turned to profitable account.

If a chlorideI solution is- It is a diicult matter to electrolytically precipitate copper from chloride solutions Without diaphragme, especially if effective regeneration of the solvent is desired. Conditions ma arise in which not only no copper is eposited, but the original cathode sheet, itself, maybe dissolved; this is largely due to the action of the regenerated :ferrie salts, and to the cupric salts and to the liberation of free chlorine. If an attempt is made to avoid the liberation of chlorine by excessive agitation of the electrolyte, the re-dissolving of the cathode copper may be increased rather than diminished; this will usually be the case. By the present method of hydrogen sulphide precipitation with a Vsimultaneous regeneration of acid, and then electrolyzing the precipitated solution in the presence of the regenerated acid to produce ferric salts, there are some advantages, and many serious difficulties are avoided, even if the end product is notthe pure electrolytic copper.

No special apparatus is required to carry out the invention, however, the electrolytic apparatus shown in my co-pending applications, Serial Nos. 145,884 and 185,652, filed February 1, 1917, and August 11, 1917, respectively is preferred for the electrolytic regeneration of the ferrie salts after the hydrogen sulphide precipitation of the metalsl and the regeneration of the acid. This regenerated acid plays an important part in the electrolytic regeneration of the solvent, and also an important part in the leaching.

In electrolyzing the solution to convert the ferrous iron into the ferrie condition, agitation is desirable during electrolysis.

etter results are also obtained by heating the solution. The best results are obtained with a fairly war'm solution and fairly energetic agitation. A temperature of 120 to 180 degrees F. will give good results. Carbon electrodes are preferred, especially with chloride solutions, for, with carbon electrodes, the depolarization, and the oxidation or adduction of the solution, is more effective than when lead, magnetite, or ferro-silicon electrodes are used, and the E. M. F. necessary for the electrolysis is appreciably reduced. The disintegration of the electrodes, under the conditions, is quite small. The heating of the solution is preferably done before the chemical reduction or precipitation, since these reactions, especially the reduction of the cupric chloride to the cuprous chloride by means ofsulphur dioxide is greatly facilitated by heating.

The equations given in the description of the process are tentative, and are only supposed in a general Way to illustrate what takes place.

1f sulphur dioxide is used preparatory to hydrogen sulphide precipitation, it is advisable to avoid an excess ofy sulphur dioxide, to avoid the precipitation of sulphur,

17. 2so2+H2s22H2o+as This may be done by providingample storage for the reduced solution, and if therel isk an excess of sulphur dioxide, enough unreduced solution, from the ore can be run into the storage tank 5, through the pipes 17 and 18 to combine with the excess of sulphur dioxide.

The accompanying drawing represents a. How sheet of the preferred method of carrying out the invention as applied to chloridesolutions, and will perhaps give a better idea of how the invention is intended to be carried out practically.

In the drawing, 1 is a leaching vat containing the ore to be treated, say, with a chloride solution. The resulting copper solution issuing from the leaching vat is iowed into the heater 2, where it is heated preparatory to the reduction with sulphur dioxide. The heatedy solution enters the reduction chamber 3, where it is treated with sulphur dioxide from the sulphur dioxide generator 4. The cupric chloride is reduced to the cuprous chloride according to equation 11, and the ferric chloride is reduced to the ferrousv chloride as shown by equationlO, with the simultaneous regeneration of acid. The reduced solution then flowsy into a storage tank 5, where more time is given for the. excess of sulphur dioxide t0 act on the solution, and fresh solution added to the reduced solution through the pipes 17 and 18 to act upon the excess of the The reduced copper solution is then drawn from the storage tank 5, in a regulated stream, into the hydrogen sulphide precipitator 6, where it is acted upon by the hydrogen sulphide from the generator 7, to precipitate the copper as the sulphide, as shown by equation 12, with the simultaneous regeneration of more acid. The regenerated acid solution together with the sulphide precipitate flows into the separator, such as a Dorr thickener, where the regenerated acid solution is separated from the sulphide precipitate. The regenerated acid solution flows through the pipe line 10, into the electrolyzer 11, where the ferrous iron is converted into the ferrie condition, as shown by equations 13, `14, 15, and

itation has been the voluminous nature ofthe sulphide. precipitatw and the. difficulties due to filtration, drying, and fusing` the dried` precipitate. l have found that these diliiculties can he overcome by' electrolyzing the precipitate sludge.- Quite a pure.. copper can he obtainedA in this Way with a` very high current, and very high energf, et?.

liciency. To carry it out practically a` certainl amount ot the rich copper solution: from the leaching. vat isv drawn firomcthe ,gr-eat deal of. sulphur would he libe-rated hy the ele'ctrolytic action, but the amount liheratedf appearstobe lquite'srnall'. AIt does not appear to correspond' Withfthe equations, p

18, CuQS I 2Cu+ S,

19. I (lu-l It appears to loef considera-bly less, and very sinall, if the mixture is agitated. It is pr'ohablethat some of the sulphur is'con verted into av soluble form-possibly into sulphuric acid-il'or itV is Well known that under certa-in conditions of electrolysis,

and especially yunder highly oxidizing in-` licences, elemental sulphurcan' be converted into sulphuric acid; The deposit isl coherent, and fairly pure; The exhausted cop` peil solutiony flowsthrough the pipe 14 into the electrolyzer l-l.. Compressed air may be drawn fromA the air receiver 20, for agitation, as desired. f

lf purer cathodes are desired than those produced in the cell l5, ca-thodesy of great purity may he obtained hy lifting thef impure cathodes outr of celll When they have sufficient copper deposited on them, and placing them' in the electrolytic refiningvl cell lo, as anodes, and refining` these anodes much the same as in regular electrolytic refining. The electrolyte in they refining tank should be a fairly pure acid* solution of' copper sulphate. The electrolyte ins cell 125 may he quite impure; thet regulan rich copper leaching solutionis prl'aferred.v

ln 'the preliminary"reduction of the iron ksalts before precipitating the copper, yeither sulphur dioxide or1 hydrogen sulphide' Will answer the purpose,` hut Vsulphur dioxide will ordinarily heI preferred, if' a preliminary reduction is desiredi lf the sulphide precipitate sludge is electrolyzed With theV rich leach* solution, there will, of course, loe considerable iron in the electrolyte; It is preferred to use the rich leach solutiony .as the ele'ctrolyte,Y because the metalcan' largely he reco'vfered'fromithe; rich leachY solution in the presence of the precipitated.. .copper sulphide With a very high efhciency, and the iron, in the electrolyte, in the electrolysis; ofthe copper sulphide precipitate, will help to bring the copper in solution during the velectrolytic action.

lilither sulphur dioxide or hydrogen sulphide will reduce the ferrie iron to the ferrouswcondition. lf hydrogen sulphide is applied to the solution Without the application of sulphur dioxide, the ferrie iron will he largely reduced before the copper is precipitated Urdinaril'y, however, the preliminary treatment with sulphur dioxide Will he preferred, for the reason that sulphur dioxide' is.i cheaply produced, regenen ates'inore acid, and the sulphide precipitate will usually he of a higher grade than when the hydrogen sulphide is applied direct.

l claim.; l y l. metallurgical process comprising leaching ores of copper With an acid solution. of ferrie iron,igenerating hydrogen sulphide from acid and ferrous sulphide, cipitating the copper from the leach solutions With the hydrogen sulphide so formed, adding the ferrous sulphate formed in the generation of the hydrogen sulphide to the leach solutions, electrolyzing the ferrous iron in thev leach solution in the presence of the regenerated acid to convert the ferrous iron into the'fer'ric condition, and then applying. the regenerated ferr-ic iron solution to the Ore.' y

2. A i metallurgical process comprisingtreatingores of copper with an acidsolutionf containing ferrie iron, generating hfdrogen sulphide fromV acid and ferrous s *lphide, adding., both the hydrogen sulphA l and the ferrousI sulphate so produced to `the leach solutions-,separating the resulting copper' sulphide precipitate from the regen-- erated acid solutions, electrolyaing the regenerated acidsolutions to convert the fen ro'usl iron into the ferrie condition, and thou applying the regenerated ferrie iron solution to the ore.

3.. Av metallurgical process comprising leachingores: ofcopperwith an acid solution of ferrioiron, precipitating the copper fromthe leach-solutions withr hydrogen sulphide, separating. the resulting` copper sulphide precipitate frointhe regenerated acid solution, electrolyaing the regenerated acid solution containing salts of iron to convert the ferrousiron into the ferrie condition, and then.v applying' the regenerated ferrie ironl solution' to the ore.

4.3 A metallurgical process comprising treating ores of copper with anacid solution 'off ferrie iron toi dissolve the` copper, treating. the resultingcopper solution Witi sulphur dioxide to reduce the salts of the variablevalent'eleznents-iin the solution from a higher to aflower valency with the simultaneous regeneration of acid, then. precipitating the copper as the sulphide with hydrogen sulphide with the simultaneous reneration of' more acid, separating the reuced and regenerated acid solution from the sulphide precipitate, and then treating the reduced solution containing salts of iron to convert the ferrous salts :into the ferrie condition, and then returning the regenerated acid ferrie salt solution to the ore.

5. A metallurgical process comprising treating ores of copper with an acid solution containing ferrie iron to dissolve the copper, precipitating the dissolved copper with hydrogen sulphide with the simultaneous regeneration of acid, separating the sulphide precipitate from the regenerated acid solution, electrolyzing the regenerated acid solution to convert the ferrous salts into the ferric condition, agitating thesolution during electrolysis, and then, when the solution is sufficiently regenerated in ferrie salts returning it to the ore.

6. A metallurgical process comprising treating ores of copper with an acid solution of ferrie iron to dissolve the copper, treating the resulting copper solution to reduce the variable valent salts in the solution from a higher to a lower valency, with the simultaneous regeneration of acid, then precipitating the copper as the sulphide with hydrogen sulphide with the simultaneous regeneration of more acid, separating the reduced and regenerated acid solution from the sulphide precipitate, and then electrolyzing the solution containing ferrous iron in the presence of the regenerated acid to convert the ferrous salts to the ferrie condi-l tion, and then returning the regenerated ferric iron solution to the ore.

7. A metallurgical `process comprising treating ores of copper with an acid solution of ferrie iron to dissolve the copper, precipitating the dissolved copper with hydrogen sulphide with the simultaneous regeneration of acid, separating the sulphide precipitate from. the regenerated acid solution. heating the solution, electrolyzing the heated regenerated acid solution to convert the ferrous salts into the ferrie condition, and then when the solution is suiiiciently regenerated in ferrie salts returning it to the ore.

8. A metallurgical process comprising treating ores of copper with an acid solution of ferrie iron to dissolve the copper, precipitating the copper with a preci'pitant capable of reducing the variable valent salts in the solution from a higher to a lower valency with the simultaneous regeneration of acid, separating the resulting precipitate from the regenerated acid solution, electrolyzing the reduced and regenerated acid solution to convert the ferrous iron to the ferrie condition, and then returning the solution to the ore. l i

9. A process, comprising treating ores of copper' with a solvent for the copper, precipitating the copper with hydrogen sulphide with the simultaneous regeneration of. acid, separating the sulphide precipitate from the regenerated acid, solution, returning the regenerated acid solution to the ore, and electrolyzing the sulphide precipitate to obtain the metal.

v10. A process comprising treating ores o' copper with an acid solution to dissolve the copper, precipitatinor the copper with `hydrogen sulphide with the simultaneous regeneration of acid, separating the sulphide precipitate from the regenerated acid solution, returning the solution to the ore, mixing the sulphide precipitate with a solution of copper, electrolyzing the mixture, and agitating the mixture during electrolysis.

1l. A process comprising treating ores of copper with an acid solution to dissolve the copper, precipitatin the copper with hydrogen sulphide wit a simultaneous regeneration of acid, electrolyzing the acid solu tion to convert the variable valent elements from a lower to a higher valency, returning the electrolyzed solution to the ore, mixing the sulphide precipitate with a copper solution, electrolyzin the mixture, and agitating the mixture c uring electrolysis.

12.'A process comprising treating ores of copper with an acid solution to extract the copper, rprecipitating the copper with hydrogen sulphide with the simultaneous regeneration of acid, returning the acid solution to the ore, mixing the sulphide precipitate with a copper solution, agitating and electrolyzing the mixture whereby the copper is deposited on the cathodes, and then removing the cathodes and electrolyzing them in a different electrolyte as the anodes to obtain the pure electrolytic metal on new cathodes.

13. A process comprising treating ores of copper with an acid solution containing ferric iron to dissolve the copper, separating the resulting copper solution from the gangue, precipitating the copper with a precipitant capable of reducing the excess of ferrie iron to the ferrous condition with a simultaneous regeneration of the acid combined with the copper, then treating the solution in the presence of the regenerated acid to raise the valency of the iron salts in the solution, and then againv applying the regenerated acid solution containing ferrie iron to the ore.

14. A ymetallurgical process comprising treating ores of copper with an acid solution to dissolve the copper, reducing the variable valent salts in the resulting copper solution from a higher tol a lower valency with sulphur dioxide, precipitating the copper from the reduced solution with hydrogen sulphide,

separating the sulphide precipitate from the plying the solution to the ore, applying the sulphide precipitate to a solvent capable of dissolving the copper and of being regenerated by the electrolysis of the copper solution, and elcctrclyzing the resulting copper solution to obtain the electrolytic metal and regenerate the solvent for the sulphide preci pitate.

24. A process comprising treating ores of .i copper with a solution containing ferrie salts to dissolve the copper, chemically pre cipitating the copper from the resulting solution, electrolyzing the precipitated solution to convert the ferrous salts into the icrric condition, returning the solution to the ore, applying the resulting chemical precipitate to a solution of ferrie salts to dissolve the copper, and electrolyzing the resulting copper solution to deposit the metal and regenerate the solvent for the chemical precipitate.

25. A process of extracting copper from its ores comprising, treating the ore with an acid chloride solution to extract the copper. chemically precipitating the copper from the resulting solution containing salts of iron with the simultaneous regeneration of acid, then treating the resulting solution freed from copper to convert the ferrous iron into the ferrie condition, and then again applying the solution to the ore.

26. A metallurgical process comprising, treating ores of copper with an acid solution containing salts of iron to dissolve the copper, separating the copper solution from the ore, chemically precipitating the copper .from the solution with a precipitant capable of regenerating acid, separating the regenerated acid solution from the copper precipitate, and then electrolyzing the regenerated acid solution freed from copper to raise the Valency of the iron salts in the solution and returning the regenerated acid and ferrie salt solution to the ore.

27. A metallurgical process comprising, treating ores of copper with an acid solution containing salts of iron to dissolve the copper, separating the copper solution from the ore, chemically precipitating the copper from the solution With a precipitant capable of regenerating acid, separating the regenerated acid solution from the copper precipitate, and then agitating the regenerated acid solution freed from copper and electrolyzing it with carbon anodes to raise the valency of the iron salts in the solution and returning the re enerated acid and ferrie salt solution to t e ore.

WILLIAM E, GREENAWALT. Witnesses:

SYLVIA PEARL J'Aoos, GEORGE C. COGHRANE. 

